Device and method for post-processing of computed tomography

ABSTRACT

A device and a method for post-processing of computed tomography (CT), which are adapted to improve an identification image of a focal nodular hyperplasia (FNH) of a liver, are provided. The method includes: obtaining the identification image including a liver contour and a non-liver contour and a Hounsfield unit (HU) value of each pixel corresponding the identification image, wherein the liver contour includes an FNH candidate contour; calculating an average HU of the liver contour; adjusting an HU value of the non-liver contour to the average HU value of the liver contour in respect with the identification image to generate a processed identification image; and updating the FNH candidate contour according to a morphological algorithm based on the processed identification image to generate an updated FNH candidate contour.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 109101870, filed on Jan. 20, 2020. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The invention relates to a device and a method, and more particularly, relates to a device and method for post-processing of computed tomography.

BACKGROUND

With the gradual popularization of deep learning, as more medical institutions are beginning to accept and look forward to use computer science for help radiologists in determining computed tomography (CT) images of patients, there are also more teams investing in development of a liver tumor identification system. Most of the current computer science and technology focuses on the identification of malignant hepatocellular carcinoma (HCC), but fails to focus on image identification of benign tumors such as hemangioma or focal nodular hyperplasia (FNH). However, for livers with several conditions, it is clearly not enough to only determining malignancies. Therefore, finding a way to determine the benign tumor of the liver to assist doctors in determining the liver condition of the patient is one of the goals of those skilled in the art.

SUMMARY

The invention provides a device and a method for post-processing of computed tomography which can improve an FNH identification image of so an FNH identification result may be closer to an actual FNH boundary and false positives of the FNH identification result may be reduced.

A device for post-processing of computed tomography of the invention is adapted to improve an identification image of a focal nodular hyperplasia (FNH) of a liver, wherein the device includes a processor, a storage medium and a transceiver. The storage medium stores a plurality of modules. The processor is coupled to the storage medium and the transceiver, and accesses and executes a plurality of modules, wherein the module include a data collection module and a computing module. The data collection module obtains the identification image regarding to a liver contour and a non-liver contour and a Hounsfield unit (HU) value of each pixel corresponding to the identification image through the transceiver, wherein the liver contour includes an FNH candidate contour. The computing module adjusts an HU value of the non-liver contour to an average HU value of the liver contour in respect with the identification image to generate a processed identification image, and updates the FNH candidate contour according to a morphological algorithm based on the processed identification image to generate an updated FNH candidate contour.

In an embodiment of the invention, the computing module determines that the updated FNH candidate contour represents a correct identification result of the FNH in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour exceeding a threshold.

In an embodiment of the invention, the computing module determines that the updated FNH candidate contour represents an incorrect identification result of the FNH in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour not exceeding a threshold.

In an embodiment of the invention, the threshold is associated with a union set of the updated FNH candidate contour and the FNH candidate contour.

In an embodiment of the invention, the morphological algorithm is an active contours without edges (ACWE) method.

A method for post-processing of computed tomography of the invention is adapted to improve an identification image of a focal nodular hyperplasia (FNH) of a liver. The method includes: obtaining the identification image regarding to a liver contour and a non-liver contour and an HU value of each pixel corresponding to the identification image, wherein the liver contour includes an FNH candidate contour; adjusting an HU value of the non-liver contour to the average HU value of the liver contour in respect with the identification image to generate a processed identification image; and updating the FNH candidate contour according to a morphological algorithm based on the processed identification image to generate an updated FNH candidate contour.

In an embodiment of the disclosure, the method further includes: determining that the updated FNH candidate contour represents an identification result of the FNH in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour exceeding a threshold.

In an embodiment of the disclosure, the method further includes: determining that the updated FNH candidate contour represents an incorrect identification result in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour not exceeding a threshold.

In an embodiment of the invention, the threshold is associated with a union set of the updated FNH candidate contour and the FNH candidate contour.

In an embodiment of the invention, the morphological algorithm is an active contours without edges (ACWE) method.

Based on the above, the device and method for post-processing of computed tomography of the invention can significantly improve the accuracy of the FNH identification. As a result, doctors will be able to more accurately determine information such as the size and location of the FNH.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a schematic diagram illustrating a device for post-processing of CT according an embodiment of the invention.

FIG. 2A is a schematic diagram illustrating an identification image of a liver having FNH according an embodiment of the invention.

FIG. 2B is a schematic diagram illustrating a processed identification image according an embodiment of the invention.

FIG. 3 is a schematic diagram illustrating an updated FNH candidate contour according to an embodiment of the invention.

FIG. 4A is a schematic diagram illustrating a processed identification image containing an incorrect FNH candidate contour according an embodiment of the invention.

FIG. 4B is a schematic diagram illustrating the updated identification image based on the incorrect FNH candidate contour according an embodiment of the invention.

FIG. 4C is a schematic diagram illustrating a processed identification image in which the incorrect updated FNH candidate contour and the FNH candidate contour are eliminated according an embodiment of the invention.

FIG. 5 is a flowchart illustrating a method for post-processing of CT according an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

FIG. 1 is a schematic diagram illustrating a device 100 for post-processing of CT according an embodiment of the invention. The device 100 is adapted to improve an identification image of a focal nodular hyperplasia (FNH) of a liver. The device 100 may include a processor 110, a storage medium 120 and a transceiver 130.

The processor 110 is, for example, a central processing unit (CPU) or other programmable micro control units (MCU) for general purpose or special purpose, a microprocessor, a digital signal processor (DSP), a programmable controller, an application specific integrated circuit (ASIC), a graphics processing unit (GPU), an arithmetic logic unit (ALU), a complex programmable logic device (CPLD), a field programmable gate array (FPGA) or other similar elements or a combination of above-mentioned elements. The processor 110 may be coupled to the storage medium 120 and the transceiver 130, and may access or execute a plurality of modules and various applications stored in the storage medium 120.

The storage medium 120 is, for example, a random access memory (RAM), a read-only memory (ROM), a flash memory, a hard disk drive (HDD), a hard disk drive (HDD), a solid state drive (SSD) or other similar elements in any stationary or movable form, or a combination of the above-mentioned elements, and is used to store the modules and various applications that may be executed by the processor 110. In this embodiment, the storage medium 120 may store the modules including a data collection module 121 and a computing module 122, ad their functions will be described later.

The transceiver 130 transmits and receives signals in a wired or wireless manner. The transceiver 130 can also perform operations such as low noise amplifying, impedance matching, frequency mixing, up and down frequency conversion, filtering, amplification and similar operations.

The data collection module 121 may obtain an identification image of a liver through the transceiver 130. FIG. 2A is a schematic diagram illustrating an identification image 10 of a liver having FNH according an embodiment of the invention. Here, the identification image 10 may include a liver contour 200 surrounding the liver parenchyma and a non-liver contour 300 surrounding the non-liver parenchyma (i.e., a black portion in FIG. 2A). The identification image 10 may also include an FNH candidate contour 250 surrounding an FNH 500. The identification image 10, the liver contour 200, the non-liver contour 300 or the FNH candidate contour 250 are generated by, for example, identifying an original liver CT image based on technologies including artificial intelligence (AI), machine learning algorithm or deep learning algorithm, but the invention is not limited thereto. In addition, the data collection module 121 may further obtain the identification image regarding to the liver and an HU (Hounsfield unit) value of each pixel corresponding to the identification image through the transceiver 130.

In general, the portion surrounded by the FNH candidate contour 250 does not completely match the FNH 500, and there may be an error between the two. In order to minimize said error, the computing module 122 may perform a post-processing on the identification image 10.

First, the computing module 122 may calculate an average HU value of the liver parenchyma in the liver contour 200 and adjust an HU value of the non-liver parenchyma in the non-liver contour 300 to the average HU value of the liver parenchyma, as shown by Equation (1), wherein P₁ represents the liver parenchyma (i.e., a set of pixels in the liver contour 200); P₂ represents the non-liver parenchyma (i.e., a set of pixels in the non-liver contour 300); x represents pixels in the identification image 10; L₀ (x) represents an unadjusted HU value of x; L₁ (x) represents an adjusted HU value of x; x_(i) represents an i-th pixel in the liver contour 200 and n represents a total of pixels in the liver contour 200.

$\begin{matrix} {{L_{1}(x)} = \left\{ \begin{matrix} {{L_{0}(x)},} & {{{if}\mspace{14mu} x} \in P_{1}} \\ {{\frac{1}{n}{\sum_{i = 1}^{n}{L_{0}\left( x_{i} \right)}}},} & {{{if}\mspace{14mu} x} \in P_{2}} \end{matrix} \right.} & (1) \end{matrix}$

FIG. 2B is a schematic diagram illustrating a processed identification image 20 according an embodiment of the invention. The computing module 122 may modify pixels in the non-liver contour 300 in the identification image 10 based on Equation (1) so that the HU value of the non-liver contour 300 is closer to the average HU value of the liver contour 200. In this way, a contrast between the non-liver parenchyma in the non-liver contour 300 and the liver parenchyma in the liver contour 200 may be reduced so that a contrast between the FNH 500 in the FNH candidate contour 250 and the liver parenchyma in the liver contour 200 becomes clearer.

Next, the computing module 122 may update the FNH candidate contour 250 according to a morphological algorithm based on the processed identification image 20 to generate an updated FNH candidate contour 251, as shown by FIG. 3. FIG. 3 is a schematic diagram illustrating the updated FNH candidate contour 251 according to an embodiment of the invention. The morphological algorithm described above is, for example, an active contours without edges (ACWE) method. First, the computing module 122 may create a regular expression of an ACWE model as shown by Equation (2), wherein F represents an energy function of the ACWE model; μ or u represents a parameter greater than or equal to 0 (in this embodiment, u=0); C represents a curve of a region boundary; length (C) is a length of C; inside (C) represents pixels inside the curve of the region boundary; c₁ represents a pixel average value of inside (C); outside (C) represents pixels outside the curve of the region boundary; c₂ represents a pixel average value of outside (C); λ₁ or λ₂ represents a parameter greater than 0 and I(x) represents a pixel value of the pixel x.

F(c ₁ ,c ₂ ,C)=μ·length(C)+ν·area(inside(C))+λ1∫_(inside)(c)∥I(x)−c ₁ ∥dx+λ ₂∫_(outside(c)) ∥I(x)−c ₂ ∥dx  (2)

Then, the computing module 122 may find a minimum value of the energy function F through iteration to solve for λ₁ and λ₂, thereby calculating a boundary closest to the FNH 500. The computing module 122 may use, for example, a level set method to track the boundary of the FNH 500, as shown by Equation (3), wherein u^(j)(x) is a level set function of the pixel x after a j-th step is performed; D_(d) represents an expansion; E_(d) represents an erosion; ∇ represents a gradient and SI_(d) oIS_(d) represents a combination of the expansion and the erosion (i.e., performing IS_(d) first (i.e., expanding before eroding to passivate for recesses) before performing SI_(d) (eroding before expanding to passivate for protrusion), λ₁ or λ₂ is a parameter greater than 0; μ is a parameter greater than or equal to 0 and I(x) is a pixel value of the pixel x. After u² (x) is calculated, the computing module 122 may determine the boundary closest to the FNH 500 (i.e., the updated FNH candidate contour 251) based on u²(x).

$\begin{matrix} \left\{ \begin{matrix} {{{u^{1}(x)} = \left\{ \begin{matrix} {1,{{{if}\mspace{11mu} {{\nabla u^{0}}}\left( {{\lambda_{1}\left( {I - c_{1}} \right)}^{2} - {\lambda_{2}\left( {I - c_{2}} \right)}^{2}} \right)(x)} < 0}} \\ {0,{{{if}\mspace{11mu} {{\nabla u^{0}}}\left( {{\lambda_{1}\left( {I - c_{1}} \right)}^{2} - {\lambda_{2}\left( {I - c_{2}} \right)}^{2}} \right)(x)} > 0}} \\ {{u^{0}(x)},{otherwise}} \end{matrix} \right.}} \\ {{{u^{2}(x)} = {\left( {\left( {{SI}_{d}{oIS}_{d}} \right)^{\mu}u^{1}} \right)(x)}}} \end{matrix} \right. & (3) \end{matrix}$

It should be noted that, an initial point of the ACWE method is selected from the FNH candidate contour predicted by AI. If AI determines the normal liver parenchyma incorrectly as the FNH, the computing module 122 may expand the updated FNH candidate contour into a region including the entire liver parenchyma according to the incorrect initial point. FIG. 4A is a schematic diagram illustrating a processed identification image 30 containing an incorrect FNH candidate contour 260 according an embodiment of the invention. FIG. 4B is a schematic diagram illustrating the updated identification image 261 based on the incorrect FNH candidate contour 260 according an embodiment of the invention. Referring to FIG. 4A and FIG. 4B together, it is assumed that AI determines a region of the normal liver parenchyma incorrectly as the incorrect FNH candidate contour 260, the computing module 122 may generate an incorrect updated FNH candidate contour 261 according to the incorrect FNH candidate contour 260 based on the ACWE method. After multiple iterative calculations, the incorrect updated FNH candidate contour 261 may be expanded to include a region including the entire normal liver parenchyma.

To avoid generating the incorrect updated FNH candidate contour, the computing module 122 may determine that the updated FNH candidate contour represents a correct FNH identification result in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour exceeding a threshold, and determine that the updated FNH candidate contour represents an incorrect FNH identification result in response to the intersection set of the updated FNH candidate contour and the FNH candidate contour not exceeding the threshold. Here, the threshold is associated with a union set of the updated FNH candidate contour and the FNH candidate contour, as shown by Equation (4) wherein Y_(AI) represents the FNH candidate contour predicted by AI; Y_(p) represents the updated FNH candidate contour calculated by the computing module 122 based on the ACWE method; T represents a constant, R=1 means that the FNH identification result is correct and R=0 means that the FNH identification result is incorrect.

$\begin{matrix} {R = \left\{ {\begin{matrix} {1,{{{{if}\mspace{11mu} Y_{AI}}\bigcap Y_{P}} > {{T \cdot Y_{AI}}\bigcup Y_{P}}}} \\ {0,{{{{if}\mspace{11mu} Y_{AI}}\bigcap Y_{P}} \leq {{T \cdot Y_{AI}}\bigcup Y_{P}}}} \end{matrix},{{\forall Y_{AI}} = 1}} \right.} & (4) \end{matrix}$

For instance, the computing module 122 may determine that the updated FNH candidate contour 251 represents a correct identification result of the FNH 500 in response to an intersection set of the updated FNH candidate contour 251 and the FNH candidate contour 250 exceeding a threshold, as shown by FIG. 3. As another example, the computing module 122 may determine that the updated FNH candidate contour 261 represents an incorrect identification result of the FNH 500 in response to the intersection set of the updated FNH candidate contour 261 and the FNH candidate contour 260 not exceeding the threshold, as shown by FIG. 4B. In order to reduce false positives of the identification result of the FNH 500, the computing module 122 may eliminate the updated FNH candidate contour 261 (and/or the FNH candidate contour 260), as shown by FIG. 4C. FIG. 4C is a schematic diagram illustrating the processed identification image 30 in which the incorrect updated FNH candidate contour 261 and the FNH candidate contour 260 are eliminated according an embodiment of the invention.

FIG. 5 is a flowchart illustrating a method for post-processing of CT according an embodiment of the invention, wherein the method may be implemented by the device 100 shown by FIG. 1. In step S501, the identification image regarding to a liver contour and a non-liver contour and an HU value of each pixel corresponding to the identification image are obtained, wherein the liver contour includes an FNH candidate contour. In step S502, an HU value of the non-liver contour is adjusted to the average HU value of the liver contour in respect with the identification image to generate a processed identification image. In step S503, the FNH candidate contour is updated according to a morphological algorithm based on the processed identification image to generate an updated FNH candidate contour.

In summary, the device and method for post-processing of computed tomography of the invention can significantly improve the accuracy of the FNH identification. The invention may regulate the non-liver contour in the identification image so that the HU value of the non-liver contour is equivalent to the average HU value of the liver contour. In this way, the difference between the HU value of the FNH and the HU value of normal parts of the liver will become clearer so that the FNH identification also becomes easier. In addition, the morphological algorithm is used to update the FNH candidate contour to make the boundary of the updated FNH candidate contour closer to the real FNH through operations such as expansion or erosion. Based on the updated FNH candidate profile, doctors will be able to more accurately determine the size and location of the FNH. On the other hand, the invention may also determine whether the updated FNH candidate contour corresponds to the correct determination result according to the intersection set or the union set of the updated FNH candidate contour and the original FNH candidate contour, so as to prevent the normal parts of the liver from being determined as the FNH to reduce false positives of the identification result.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents. 

What is claimed is:
 1. A device for post-processing of computed tomography, adapted to improve an identification image of a focal nodular hyperplasia (FNH) of a liver, wherein the device comprises: a transceiver; a storage medium, storing a plurality of modules; and a processor, coupled to the storage medium and the transceiver, and accessing and executing a plurality of modules, wherein the modules comprises: a data collection module, configured to obtain the identification image regarding to a liver contour and a non-liver contour, and a Hounsfield unit (HU) value of each pixel corresponding to the identification image through the transceiver, wherein the liver contour comprises an FNH candidate contour; and a computing module, configured to adjust an HU value of the non-liver contour to an average HU value of the liver contour in respect with the identification image to generate a processed identification image, and updating the FNH candidate contour according to a morphological algorithm based on the processed identification image to generate an updated FNH candidate contour.
 2. The device according to claim 1, wherein the computing module determines that the updated FNH candidate contour represents a correct identification result of the FNH in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour exceeding a threshold.
 3. The device according to claim 1, wherein the computing module determines that the updated FNH candidate contour represents an incorrect identification result of the FNH in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour not exceeding a threshold.
 4. The device according to claim 2, wherein the threshold is associated with a union set of the updated FNH candidate contour and the FNH candidate contour.
 5. The device according to claim 1, wherein the morphological algorithm is an active contours without edges (ACWE) method.
 6. A method for post-processing of computed tomography, adapted to improve an identification image of a focal nodular hyperplasia (FNH) of a liver, wherein the method comprises: obtaining the identification image regarding to a liver contour and a non-liver contour and an HU value of each pixel corresponding to the identification image, wherein the liver contour comprises an FNH candidate contour; adjusting an HU value of the non-liver contour to an average HU value of the liver contour in respect with the identification image to generate a processed identification image; and updating the FNH candidate contour according to a morphological algorithm based on the processed identification image to generate an updated FNH candidate contour.
 7. The method according to claim 6, further comprising: determining that the updated FNH candidate contour represents an identification result of the FNH in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour exceeding a threshold.
 8. The method according to claim 6, further comprising: determining that the updated FNH candidate contour represents an incorrect identification result in response to an intersection set of the updated FNH candidate contour and the FNH candidate contour not exceeding a threshold.
 9. The method according to claim 7, wherein the threshold is associated with a union set of the updated FNH candidate contour and the FNH candidate contour.
 10. The method according to claim 6, wherein the morphological algorithm is an active contours without edges (ACWE) method. 